Search

C30 carotenoids, which have shorter backbones than C40 carotenoids, are known to be produced in the pathogenic bacterium Staphylococcus aureus that causes opportunistic infection. The first committed enzyme in the C30 carotenoid synthetic pathway is dehydrosqualene synthase CrtM. CrtM converts farnesyl pyrophosphate to dehydrosqualene. Dehydrosqualene desaturase CrtN then converts dehydrosqualene to the yellow C30 carotenoid, 4,4'-diaponeurosporene. This chapter describes a method to synthesize C30 carotenoids in Bacillus subtilis, which is generally recognized as a safe (GRAS) organism. Introduction of S. aureus crtM and crtN genes into B. subtilis results in yellow pigmentation. The B. subtilis transformant accumulates two C30 carotenoids, 4,4'-diapolycopene and 4,4'-diaponeurosporene. Furthermore, together with crtMN, introduction of S. aureus crtP and crtQ genes, which encode mixed function oxidase and glycosyltransferase, respectively, donates the ability to produce glycosylated C30 carotenoic acid. Thus, carotenoid biosynthesis genes of S. aureus is applicable to genetically modify B. subtilis in order to construct a safe organism producing C30 carotenoids.

Pseudomonas oxalaticus OX1 carrying recombinant plasmid pFUS and 29 gram-negative bacteria were used as donor and recipients, respectively, for conjugations. The plasmid pFUS contains genes necessary for chemolithoautotrophic growth in a hydrogen-oxidizing bacterium Alcaligenes hydrogenophilus. By the conjugal transfer of plasmid pFUS, 12 strains acquired the ability to grow in a mineral salts medium under a gas mixture containing H2’O2’, and CO2. Pseudomonas cepacia carrying pFUS had hydrogenase and ribulose-1,5-bisphosphate carboxylase activities, and could grow at a rate almost equivalent to the growth rates of ordinary hydrogen-oxidizing bacteria. Pseudomonas acidophila carrying plasmid pFUS expressed indigenous antibiotic secretion under chemolithoautotrophic conditions. Plasmid pFUS could be stably maintained in these strains in the absence of selection pressure created by the addition of an antibiotic or chemolithoautotrophic conditions. This study shows that introduction of DNA fragments responsible for chemolithoautotrophic growth into a producer of valuable substances could be a promising technique for CO2recycling.

A marine photosynthetic bacterium Rhodopseudomonas sp. strain W-1S, accumulated polyhydroxybutyrate (PHB) to 56% of the dry cell weight under microaerobic and photoheterotrophic conditions. The addition of NaC1 and phosphate was essential for the accumulation. Acetate was the best carbon source for PHB accumulation, whereas adding malate, succinate, or sugars that did not support the growth in this strain resulted in no accumulation. The strain accumulated PHB to about 50% of the dry cell weight at the logarithmic phase of growth. These results suggested that the accumulation would be growth associated under microaerobic and photoheterotrophic conditions. Vitamins, especially biotin, exerted an inhibitory effect on PHB accumulation and a stimulatory effect on pigment production. There might be regulation of carbon flux to PHB or pigments as storage materials.